The present invention relates to installations for producing nonwoven webs.
An installation for producing a nonwoven web is already known that comprises, in succession from the top down, a generator of a curtain of filaments, especially plastic filaments, a slot attenuator for attenuating the filaments of the curtain followed, at a distance from the lower edge of the attenuating slot attenuator, by a diffuser and a conveyor for collecting the filaments exiting the diffuser.
The generator of a curtain of filaments usually comprises an extruder intended to extrude a molten organic polymer through a spinneret drilled with numerous holes so as to form a curtain of filaments and, beneath the spinneret, a device for cooling the curtain of filaments. The slot attenuator for attenuating the filaments of the curtain generally has opposed sidewalls and opposed endwalls that define an oblong inlet slot for receiving the filaments and an oblong outlet slot from which the filaments exit. A slot-shaped passage extends between the inlet and the outlet and the filaments pass through it, being attenuated by the injection of a stream of air into the slot-shaped passage, which stream is sufficient to attenuate the filaments. Beneath this slot attenuator for attenuating the filaments of the curtain is the diffuser, which is intended to spread out the incoming curtain. Since the diffuser diverges or is flared downward, the curtain that passes through it progressively spreads out as it falls. The web that thus forms on the collecting conveyor placed beneath the diffuser should be more uniform.
It turns out in practice that this uniformity as defined for example by the weight per m2 of the web is not achieved as well as would be liked.